Transmission of acknowledgement signals in a communication system

ABSTRACT

Methods and apparatus are described for a User Equipment (UE) to transmit a variable number of HARQ-ACK bits in response to the reception of Transport Blocks (TBs) in multiple DownLink (DL) Component Carriers (CCs). The resources for the transmission of an HARQ-ACK signal in response to the reception of TBs in each DL CC are determined from the resources used for the transmission of the respective Scheduling Assignment (SA) in that DL CC. In order to increase the multiplexing capacity of HARQ-ACK bits in a single HARQ-ACK signal, the UE may use more than one of the resources determined from the resources used for the transmission of the SA in each DL CC. The UE may also adapt the parameters for the transmission of HARQ-ACK bits depending on their number.

This application is a U.S. national stage application of InternationalApplication No. PCT/KR2010/001541, filed on Mar. 11, 2010, which claimspriority to U.S. Provisional Application No. 61/159,229, filed on Mar.11, 2009, the contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention is directed to wireless communication systems and,more specifically, to the transmission of acknowledgment signals in theuplink of a communication system.

BACKGROUND ART

A communication system consists of the DownLink (DL), conveyingtransmissions of signals from a base station (Node B) to User Equipments(UEs), and of the UpLink (UL), conveying transmissions of signals fromUEs to the Node B. A UE, also commonly referred to as a terminal or amobile station, may be fixed or mobile and may be a wireless device, acellular phone, a personal computer device, etc. A Node B is generally afixed station and may also be referred to as a Base Transceiver System(BTS), an access point, or some other terminology.

The UL signals consist of data signals, carrying the informationcontent, control signals, and Reference Signals (RS), which are alsoknown as pilot signals. The UEs convey UL data signals through aPhysical Uplink Shared CHannel (PUSCH). The UL control signals includeacknowledgement signals associated with the application of HybridAutomatic Repeat reQuest (HARQ) and other control signals. A UEtransmits an HARQ-ACKnowledgement (HARQ-ACK) signal in response to thereception of Transport Blocks (TBs). Depending on whether the receptionof a TB is correct or incorrect, the respective HARQ-ACK bit is an ACKor a NAK which can be respectively represented by a bit value of “1” ora bit value of “0”. The HARQ-ACK signal is transmitted over aTransmission Time Interval (TTI) either in a Physical Uplink ControlCHannel (PUCCH) or, together with data, in the PUSCH.

An exemplary structure for the PUCCH transmission in a TTI, which forsimplicity is assumed to consist of one sub-frame, is shown in FIG. 1.The sub-frame 110 includes two slots. Each slot 120 includes

-   N_(symb) ^(UL)

symbols used for the transmission of HARQ-ACK signals or ReferenceSignals (RS). Each symbol 130 further includes a Cyclic Prefix (CP) tomitigate interference due to channel propagation effects. The PUCCHtransmission in the first slot may be at a different part of theoperating BandWidth (BW) than the PUCCH transmission in the second slot.Some symbols in each slot can be used for RS transmission to providechannel estimation and enable coherent demodulation of the receivedHARQ-ACK signal. The transmission BW is assumed to consist of frequencyresource units which will be referred to as Physical Resource Blocks(PRBs). Each PRB is further assumed to consist of

-   N_(sc) ^(RB)-   sub-carriers, or Resource Elements (REs), and a UE transmits its    HARQ-ACK signals over one PRB 140 in the PUCCH.

An exemplary structure for the HARQ-ACK signal transmission in one ofthe subframe slots is illustrated in FIG. 2. The transmission structure210 comprises of HARQ-ACK signals and RS to enable coherent demodulationof the HARQ-ACK signals. The HARQ-ACK bits 220 modulate 230 a “ConstantAmplitude Zero Auto-Correlation (CAZAC)” sequence 240, for example withBinary Phase Shift Keying (BPSK) for 1 HARQ-ACK bit or with QuadraturePhase Shift Keying (QPSK) for 2 HARQ-ACK bits which is then transmittedafter performing the Inverse Fast Fourier Transform (IFFT) operation asit is subsequently described. Each RS 250 is transmitted through theunmodulated CAZAC sequence. The signal transmission in FIG. 2 iscontiguous in frequency and is referred to as Single-Carrier (SC)transmission.

An example of CAZAC sequences is given by

${c_{k}(n)} = {\exp\left\lbrack {\frac{{j2\pi}\; k}{Z}\left( {n + {n\frac{n + 1}{2}}} \right)} \right\rbrack}$

where

-   Z

is the length of the CAZAC sequence,

-   n

is the index of an element of the sequence

-   n={0, 1, . . . , Z−1},

and

-   k

is the index of the sequence. If

-   Z

is a prime integer, there are

-   Z−1

distinct sequences which are defined as

-   k

ranges in

-   {0, 1, . . . , Z−1}.

If the PRBs comprise of an even number of REs, such as for example

-   N_(sc) ^(RB)=12-   REs, CAZAC sequences with even length can be directly generated    through computer search for sequences satisfying the CAZAC    properties.

FIG. 3 shows an exemplary transmitter structure for a CAZAC sequencethat can be used without modulation as RS or with BPSK or QPSKmodulation as HARQ-ACK signal. The frequency-domain version of acomputer generated CAZAC sequence 310 is used. The REs corresponding tothe assigned PUCCH BW are selected 320 for mapping 330 the CAZACsequence, an IFFT is performed 340, and a Cyclic Shift (CS) applies tothe output 350 as it is subsequently described. Finally, the cyclicprefix (CP) 360 and filtering 370 are applied to the transmitted signal380. Zero padding is assumed to be inserted by the reference UE in REsused for the signal transmission by other UEs and in guard REs (notshown). Moreover, for brevity, additional transmitter circuitry such asdigital-to-analog converter, analog filters, amplifiers, and transmitterantennas as they are known in the art, are not shown.

The reverse (complementary) transmitter functions are performed for thereception of the CAZAC sequence. This is conceptually illustrated inFIG. 4 where the reverse operations of those in FIG. 3 apply. An antennareceives RF analog signal and after further processing units (such asfilters, amplifiers, frequency down-converters, and analog-to-digitalconverters) the digital received signal 410 is filtered 420 and the CPis removed 430. Subsequently, the CS is restored 440, a Fast FourierTransform (FFT) 450 is applied, and the transmitted REs 460 are selected465. FIG. 4 also shows the subsequent correlation 470 with the replica480 of the CAZAC sequence. Finally, the output 490 is obtained which canthen be passed to a channel estimation unit, such as a time-frequencyinterpolator, in case of a RS, or can to detect the transmittedinformation, in case the CAZAC sequence is modulated by HARQ-ACK bits.

Different CSs of the same CAZAC sequence provide orthogonal CAZACsequences. Therefore, different CSs of the same CAZAC sequence can beallocated to different UEs in the same PUCCH PRB and achieve orthogonalmultiplexing for the respective HARQ-ACK signal transmissions. Thisprinciple is illustrated in FIG. 5. In order for the multiple CAZACsequences 510, 530, 550, 570 generated correspondingly from multiple CSs520, 540, 560, 580 of the same root CAZAC sequence to be orthogonal, theCS value

-   Δ

590 should exceed the channel propagation delay spread

-   D

(including a time uncertainty error and filter spillover effects). If

-   T_(s)-   is the symbol duration, the number of such CSs is └T_(s)/D┘,-   where the-   └ ┘-   (floor) function rounds a number to its previous integer. Orthogonal    multiplexing can also be in the time domain using Orthogonal    Covering Codes (OCC). The symbols for HARQ-ACK and RS transmission    in each slot are respectively multiplied with a first OCC and a    second OCC but further details are omitted for brevity as these    multiplexing aspects are not material to the invention. The number    of resources in a PUCCH PRB is determined by the product of the    number of CS for the CAZAC sequence times the OCC length. For 6 CS,    length 4 OCC for the symbols used for HARQ-ACK signal transmission,    and length 3 OCC for the symbols used for RS transmission, the    number of resources for HARQ-ACK signaling in a PRB is 6×3=18 (the    smaller OCC length applies).

A UE can determine the PUCCH resource (PRB, CS, OCC) for its HARQ-ACKsignal transmission either through explicit indication from its servingNode B or through implicit indication. The latter can be based on theresources used for the transmission of the Scheduling Assignment (SA) inthe Physical Downlink Control CHannel (PDCCH). The SA configures theparameters for the reception by the UE of TBs in response to which theUE subsequently transmits an HARQ-ACK signal. An exemplary PDCCHtransmission considers that the REs carrying each SA are grouped intoControl Channel Elements (CCEs). For a given number of SA informationbits, the number of CCEs depends on the channel coding rate (QPSKmodulation is assumed). For a UE with low Signal-to-Interference andNoise Ratio (SINR), the Node B may use a low channel coding rate toachieve a desired BLock Error Rate (BLER) while it may use a high codingrate for a UE with high SINR. Therefore, a SA may require more CCEs forits transmission to a low SINR UE. Typical CCE aggregation levels followa “tree-based” structure consisting, for example, of 1, 2, 4, and 8CCEs.

FIG. 6 further illustrates the PDCCH transmission using CCEs. Afterchannel coding and rate matching of the SA information bits (not shown),the encoded SA bits are mapped to CCEs in the logical domain. The first4 CCEs, CCE1 601, CCE2 602, CCE3 603, and CCE4 604 are used for the SAtransmission to UE1. The next 2 CCEs, CCE5 611 and CCE6 612, are usedfor the SA transmission to UE2. The next 2 CCEs, CCE7 621 and CCE8 622,are used for the SA transmission to UE3. Finally, the last CCE, CCE9631, is used for the SA transmission to UE4. After further processingwhich can include bit scrambling, modulation, interleaving, and mappingto REs 640, each SA is transmitted in the PDCCH 650.

At the UE receiver, the reverse operations are performed (not shown forbrevity) and if the SA is correctly decoded, the UE proceeds to receivethe TBs. A one-to-one mapping exists between the PUCCH resources forHARQ-ACK signal transmission and the CCEs used for the SA transmission.For example, if a single PUCCH resource is used for HARQ-ACK signaltransmission, it may correspond to the CCE with the lowest index (firstCCE) for the respective SA. Then, UE1, UE2, UE3, and UE4 userespectively PUCCH resource 1, 5, 7, and 9 for their HARQ-ACK signaltransmission. If all resources within a PUCCH PRB are used, theresources in the immediately next PRB can be used. The first PUCCH PRBfor HARQ-ACK signal transmission may be informed by the serving Node Bthrough broadcast signaling.

In order to support higher data rates and improve the spectralefficiency relative to legacy communication systems, BWs larger than theones of Component Carriers (CCs) for legacy systems are needed. Theselarger BWs may be achieved by the aggregation of multiple legacy CCs.For example, a BW of 100 MHz may be achieved by aggregating five 20 MHzCCs. The reception of TBs in each DL CC is configured by a respective SAas described in FIG. 6.

Each DL CC is associated with an UL CC which contains respectiveresources for the HARQ-ACK signal transmission. In case each differentDL CC is linked to a different UL CC, the resources for HARQ-ACK signaltransmission may be as for the legacy systems. In case multiple DL CCsare linked to the same UL CC for HARQ-ACK signal transmission, separateresources may be pre-assigned in the UL CC for the transmission ofHARQ-ACK signals in response to TBs in each of the DL CCs. This isfurther illustrated in FIG. 7 where two DL CCs, 710 and 720, are linkedto one UL CC 730 and the resources for the HARQ-ACK signal transmissionin response to TBs transmitted in the first DL CC are always in a firstset of UL resources 740 while the resources for the HARQ-ACKtransmission in response to TBs transmitted in the second DL CC arealways in a second set of UL resources 750.

The conventional approach for a UE to transmit HARQ-ACK signals inresponse to the reception of TBs in multiple DL CCs is to simply extendthe HARQ-ACK signaling method in case of a single DL CC andsimultaneously transmit multiple HARQ-ACK signals, each corresponding toa DL CC. The main disadvantage of this approach stems for the limitationin the maximum UE transmission power. Simultaneous transmission ofmultiple HARQ-ACK signals increases the peak-to-average power ratio(PAPR) of the combined signal transmission as the single-carrierproperty is not preserved. Also, channel estimation becomes worse as theRS power is distributed in multiple resources and the total interferenceis increased as HARQ-ACK signals are transmitted in multiple resources.

In order to address the previous shortcomings for the transmission ofmultiple HARQ-ACK signals, an alternative method is to transmit a singleHARQ-ACK signal while selecting the transmission resources to provideadditional degrees of freedom and hence allow for more HARQ-ACKinformation to be implicitly conveyed. For example, if the UE receives asingle TB in each of four DL CCs and each DL CC is linked to a differentUL CC then, by selecting the UL CC where the HARQ-ACK signal istransmitted, the UE can convey 2 HARQ-ACK bits and convey the remaining2 HARQ-ACK bits by applying QPSK modulation to the transmitted HARQ-ACKsignal. Although this CC selection method avoids the shortcomings ofmultiple simultaneous HARQ-ACK signal transmissions, it cannot generallyprovide adequate multiplexing capacity. For example, if the UE receivestwo TBs in any of the four DL CCs, then at least 5 HARQ-ACK bits willneed to be transmitted which is not possible using only UL CC selectionand QPSK modulation. Moreover, having a variable UL CC convey theHARQ-ACK signal transmission is not desirable for implementation andperformance reasons.

Therefore, there is a need to determine transmission methods forHARQ-ACK signals in response to TBs transmitted in multiple DL CCs thatavoid increasing the PAPR and also avoid degrading the receptionreliability of the HARQ-ACK signal while providing the requiredmultiplexing capacity for the transmission of the HARQ-ACK bits.

There is another need to minimize the interference generated by theHARQ-ACK signal transmission and minimize the respective requiredresources by avoiding the transmission of multiple HARQ-ACK signals perUE transmitter antenna.

There is another need to determine rules for applying differentprinciples to the transmission of a single HARQ-ACK signal depending onthe number of HARQ-ACK bits that need to be conveyed.

DISCLOSURE OF INVENTION Technical Problem

Accordingly, the present invention has been designed to solve at leastthe afore-mentioned limitations and problems in the prior art and thepresent invention provides methods and apparatus for a UE to transmitACKnowledgement signals associated with the use of a Hybrid AutomaticRepeat reQuest (HARM) process (HARQ-ACK signals) that are in response tothe reception by the UE of Transport Blocks (TBs) transmitted by a NodeB in multiple Component Carriers (CCs).

Solution to Problem

In accordance with a first embodiment of the present invention, the UEadapts the modulation scheme of each HARQ-ACK signal, or the duration ofeach HARQ-ACK signal conveying different HARQ-ACK bits within aTransmission Time Interval (TTI), or the resources used by each HARQ-ACKsignal, or whether HARQ-ACK bits are bundled, according to the totalnumber of HARQ-ACK bits the UE conveys within the TTI.

In accordance with a second embodiment of the present invention, the UEreceives multiple Scheduling Assignments (SAs) from the Node B with eachSA informing the UE of the transmission from the Node B of TBs in arespective CC. A set of Control Channel Elements (CCEs) conveys each SA.Each CCE determines a resource for HARQ-ACK signal transmission. If thenumber of HARQ-ACK bits the UE transmits within a TTI is smaller than orequal to a predetermined value, the UE uses only the first CCE from eachSA to determine the resources for HARQ-ACK signal transmission.Otherwise, the UE uses additional CCEs from at least one SA to determinethe resources for HARQ-ACK signal transmission. In the latter case, theUE may use all CCEs from all SAs to determine the resources for HARQ-ACKsignal transmission.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects, features, and advantages of the presentinvention will be more apparent from the following detailed descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram illustrating an exemplary PUCCH sub-frame structure;

FIG. 2 is a diagram illustrating an exemplary structure for HARQ-ACKsignal transmission in one slot of a PUCCH sub-frame;

FIG. 3 is a block diagram illustrating an exemplary transmitterstructure for a CAZAC sequence;

FIG. 4 is a block diagram illustrating an exemplary receiver structurefor a CAZAC sequence;

FIG. 5 is a diagram illustrating an exemplary multiplexing of CAZACsequences through the application of different cyclic shifts;

FIG. 6 is a block diagram illustrating the PDCCH transmission usingCCEs;

FIG. 7 is a diagram illustrating the availability of different resourcesfor HARQ-ACK signal transmission in an UL CC in response to reception ofTBs in multiple DL CCs;

FIG. 8 is a diagram illustrating the generation of resources forHARQ-ACK signal transmission using the CCEs that convey the SAs for thereception of TBs in multiple DL CCs.

FIG. 9 is a diagram illustrating a first exemplary parameter selectionprocess for the HARQ-ACK signal transmission method depending on thenumber of HARQ-ACK bits; and

FIG. 10 is a diagram illustrating a second exemplary parameter selectionprocess for the HARQ-ACK signal transmission method depending on thenumber of HARQ-ACK bits.

MODE FOR THE INVENTION

The present invention will now be described more fully hereinafter withreference to the accompanying drawings. This invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein. Rather, these embodiments areprovided so that this disclosure will be thorough and complete and willfully convey the scope of the invention to those skilled in the art.

Additionally, although the present invention is described in relation toan Orthogonal Frequency Division Multiple Access (OFDMA) communicationsystem, it also applies to all Frequency Division Multiplexing (FDM)systems in general and to Single-Carrier Frequency Division MultipleAccess (SC-FDMA), OFDM, FDMA, Discrete Fourier Transform (DFT)-spreadOFDM, DFT-spread OFDMA, SC-FDMA, and SC-OFDM in particular.

Methods and apparatus are described for increasing the informationmultiplexing capacity in a single HARQ-ACK signal transmitted from a UEin response to the reception of TBs in multiple DL CCs. It is assumedthat for each DL CC, separate PUCCH resources exist for the HARQ-ACKsignal transmission in response to reception of TBs in the respective DLCC.

The present invention considers that the UE can select the resources forthe transmission of the HARQ-ACK signal based on the value of thetransmitted HARQ-ACK bits. These resources are not necessarily confinedto the ones corresponding to HARQ-ACK signal transmission from a singleDL CC but combinations of resources corresponding to multiple DL CCs canbe used for the transmission of a single HARQ-ACK signal in each of thesub-frame slots. These resources are derived from some or all PDCCH CCEs(not necessarily from only the first CCE) used to transmit the SAsassociated with the reception of TBs over

-   N

DL CCs for which HARQ-ACK information is subsequently generated andtransmitted by the UE to its serving Node B. For example, for thetransmission of SAs associated with the application of the MultipleInput Multiple Output (MIMO) transmission principle wherein the Node Bcan convey multiple TBs to a UE in a sub-frame of the same DL CC, thesize of the SA is typically large enough so that of 2 PDCCH CCEs can bealways assumed for its transmission. The number of available resourcesfor the transmission of an HARQ-ACK signal is

$T = {\sum\limits_{j = 1}^{N}K_{j}}$where K_(j)

-   where-   K_(j)-   is the number of CCEs used for the SA transmission in the-   j^(th) DL CC, j=1, . . . , N.

In addition, the sub-frame slots may also contribute in the total numberof available resources if either the same CS in each of the

-   L=2

sub-frame slots is used for two combinations of HARQ-ACK bits havinglength-2 OCC in each slot or if different HARQ-ACK bits are transmittedin each sub-frame slot as they will be subsequently described.

FIG. 8 further illustrates the concept for generating

-   T=8

UL resources for the transmission by a reference UE of an HARQ-ACKsignal is response to the reception of TBs over

-   N=3

DL CCs, DL CC1 802, DL CC2 804, and DL CC3 806. The SAs associated withthe reception of TBs in each of the DL CCs are assumed to be separatelyencoded and transmitted in the respective DL CC but this is not alimiting aspect of the invention and joint coding and transmission ofthe SAs may also be used. In the PDCCH of DL CC1, the SA transmission tothe reference UE, UEr 810, is allocated

-   K₁=2

CCEs, CCE i and CCE i+1 820. The remaining CCEs in the PDCCH of DL CC1are allocated to other UEs 811A and 811B. In the PDCCH of DL CC2, the SAtransmission to the reference UE, UEr 812, is allocated

-   K₂=2

CCEs, CCE k and CCE k+1 822. The remaining CCEs are allocated to otherUEs 813A and 813B. In the PDCCH of DL CC3, the SA transmission to thereference UE, UEr 814, is allocated

-   K₃=4

CCEs, CCE 1, CCE 1+1, CCE 1+2, and CCE 1+3 824. The remaining CCEs areallocated to other UEs 825A and 825B. Using a one-to-one mapping, theCCEs in the PDCCH of DL CC1, the PDCCH of DL CC2, and the PDCCH of DLCC3 are respectively mapped, 830, 832, and 834, to the respective ULresources for the transmission of HARQ-ACK signals, 840 for UEr and 841Aand 841B for other UEs, 842 for UEr and 843A and 843B for other UEs, and844 for UEr and 845A and 845B for other UEs. The total resources (RSRC)available for the transmission of an ACK/NAK channel from the referenceUE are {RSRC i, RSRC i+1, RSRC k, RSRC k+1, RSRC i, RSRC i+1, RSRC k,RSRC k+1} for a total of

$T = {{\sum\limits_{j = 1}^{3}K_{j}} = 8}$

-   resources.

A first mechanism for increasing the multiplexing capacity of a singleHARQ-ACK signal, in terms of the number of HARQ-ACK bits it can conveyper UE, is to allow the same resource to be used in one of the two slotsfor the transmission of different HARQ-ACK bits (the resource may bedifferent in the two slots). Then, for

-   L=2

slots in the exemplary embodiment, the total number of resourcecombinations is

-   T^(L).

The total number of combinations for the values of

-   M

HARQ-ACK bits is

-   2^(M).

Resource selection with QPSK modulation can support the transmission of

-   M

HARQ-ACK bits if

-   2^(M-2)≦T^(L).

Table 1 illustrates the transmission of

-   M=8

HARQ-ACK bits assuming

-   N=4

DL CCs,

-   K_(j)=2 CCEs (j=1, . . . , N),

and

-   L=2

slots for the transmission of the SA in each DL CC. Therefore,

-   T=8, T^(L)=64, and 2^(M-2)=64.

TABLE 1 Mapping of HARQ-ACK Bits to Resources - Single HARQ-ACK SignalTransmission. ACK → −1, NAK → 1 DL CC Link of UL Resources DL CC Link ofUL Resources Combinations of Bits for Transmission in 1^(st) Slot forTransmission in 2^(nd) Slot {1, 1, 1, 1, 1, 1} DL CC1, CCE1 (Resource 1)DL CC1, CCE1 (Resource 1) {1, 1, 1, 1, 1, −1} DL CC1, CCE1 (Resource 1)DL CC1, CCE2 (Resource 2) {1, 1, 1, 1, −1, 1} DL CC1, CCE1 (Resource 1)DL CC2, CCE1 (Resource 3) {1, 1, 1, 1, −1, −1} DL CC1, CCE1 (Resource 1)DL CC2, CCE2 (Resource 4) {1, 1, 1, −1, 1, 1} DL CC1, CCE1 (Resource 1)DL CC3, CCE1 (Resource 5) {1, 1, 1, −1, 1, −1} DL CC1, CCE1 (Resource 1)DL CC3, CCE2 (Resource 6) {1, 1, 1, −1, −1, 1} DL CC1, CCE1 (Resource 1)DL CC4, CCE1 (Resource 7) {1, 1, 1, −1, −1, −1} DL CC1, CCE1(Resource 1) DL CC4, CCE2 (Resource 8) {1, 1, −1, 1, 1, 1} DL CC1, CCE2(Resource 2) DL CC1, CCE1 (Resource 1) {1, 1, −1, 1, 1, −1} DL CC1, CCE2(Resource 2) DL CC1, CCE2 (Resource 2) {1, 1, −1, 1, −1, 1} DL CC1, CCE2(Resource 2) DL CC2, CCE1 (Resource 3) {1, 1, −1, 1, −1, −1} DL CC1,CCE2 (Resource 2) DL CC2, CCE2 (Resource 4) {1, 1, −1, −1, 1, 1} DL CC1,CCE2 (Resource 2) DL CC3, CCE1 (Resource 5) {1, 1, −1, −1, 1, −1} DLCC1, CCE2 (Resource 2) DL CC3, CCE2 (Resource 6) {1, 1, −1, −1, −1, 1}DL CC1, CCE2 (Resource 2) DL CC4, CCE1 (Resource 7) {1, 1, −1, −1, −1,−1} DL CC1, CCE2 (Resource 2) DL CC4, CCE2 (Resource 8) {1, −1, 1, 1, 1,1} DL CC2, CCE1 (Resource 3) DL CC1, CCE1 (Resource 1) {1, −1, 1, 1, 1,−1} DL CC2, CCE1 (Resource 3) DL CC1, CCE2 (Resource 2) {1, −1, 1, 1,−1, 1} DL CC2, CCE1 (Resource 3) DL CC2, CCE1 (Resource 3) {1, −1, 1, 1,−1, −1} DL CC2, CCE1 (Resource 3) DL CC2, CCE2 (Resource 4) {1, −1, 1,−1, 1, 1} DL CC2, CCE1 (Resource 3) DL CC3, CCE1 (Resource 5) {1, −1, 1,−1, 1, −1} DL CC2, CCE1 (Resource 3) DL CC3, CCE2 (Resource 6) {1, −1,1, −1, −1, 1} DL CC2, CCE1 (Resource 3) DL CC4, CCE1 (Resource 7) {1,−1, 1, −1, −1, −1} DL CC2, CCE1 (Resource 3) DL CC4, CCE2 (Resource 8){1, −1, −1, 1, 1, 1} DL CC2, CCE2 (Resource 4) DL CC1, CCE1 (Resource 1){1, −1, −1, 1, 1, −1} DL CC2, CCE2 (Resource 4) DL CC1, CCE2 (Resource2) {1, −1, −1, 1, −1, 1} DL CC2, CCE2 (Resource 4) DL CC2, CCE1(Resource 3) {1, −1, −1, 1, −1, −1} DL CC2, CCE2 (Resource 4) DL CC2,CCE2 (Resource 4) {1, −1, −1, −1, 1, 1} DL CC2, CCE2 (Resource 4) DLCC3, CCE1 (Resource 5) {1, −1, −1, −1, 1, −1} DL CC2, CCE2 (Resource 4)DL CC3, CCE2 (Resource 6) {1, −1, −1, −1, −1, 1} DL CC2, CCE2 (Resource4) DL CC4, CCE1 (Resource 7) {1, −1, −1, −1, −1, −1} DL CC2, CCE2(Resource 4) DL CC4, CCE2 (Resource 8) {−1, 1, 1, 1, 1, 1} DL CC3, CCE1(Resource 5) DL CC1, CCE1 (Resource 1) {−1, 1, 1, 1, 1, −1} DL CC3, CCE1(Resource 5) DL CC1, CCE2 (Resource 2) {−1, 1, 1, 1, −1, 1} DL CC3, CCE1(Resource 5) DL CC2, CCE1 (Resource 3) {−1, 1, 1, 1, −1, −1} DL CC3,CCE1 (Resource 5) DL CC2, CCE2 (Resource 4) {−1, 1, 1, −1, 1, 1} DL CC3,CCE1 (Resource 5) DL CCS, CCE1 (Resource 5) {−1, 1, 1, −1, 1, −1} DLCC3, CCE1 (Resource 5) DL CC3, CCE2 (Resource 6) {−1, 1, 1, −1, −1, 1}DL CC3, CCE1 (Resource 5) DL CC4, CCE1 (Resource 7) {−1, 1, 1, −1, −1,−1} DL CC3, CCE1 (Resource 5) DL CC4, CCE2 (Resource 8) {−1, 1, −1, 1,1, 1} DL CC3, CCE2 (Resource 6) DL CC1, CCE1 (Resource 1) {−1, 1, −1, 1,1, −1} DL CC3, CCE2 (Resource 6) DL CC1, CCE2 (Resource 2) {−1, 1, −1,1, −1, 1} DL CC3, CCE2 (Resource 6) DL CC2, CCE1 (Resource 3) {−1, 1,−1, 1, −1, −1} DL CC3, CCE2 (Resource 6) DL CC2, CCE2 (Resource 4) {−1,1, −1, −1, 1, 1} DL CC3, CCE2 (Resource 6) DL CC3, CCE1 (Resource 5){−1, 1, −1, −1, 1, −1} DL CC3, CCE2 (Resource 6) DL CC3, CCE2 (Resource6) {−1, 1, −1, −1, −1, 1} DL CC3, CCE2 (Resource 6) DL CC4, CCE1(Resource 7) {−1, 1, −1, −1, −1, −1} DL CC3, CCE2 (Resource 6) DL CC4,CCE2 (Resource 8) {−1, −1, 1, 1, 1, 1} DL CC4, CCE1 (Resource 7) DL CC1,CCE1 (Resource 1) {−1, −1, 1, 1, 1, −1} DL CC4, CCE1 (Resource 7) DLCC1, CCE2 (Resource 2) {−1, −1, 1, 1, −1, 1} DL CC4, CCE1 (Resource 7)DL CC2, CCE1 (Resource 3) {−1, −1, 1, 1, −1, −1} DL CC4, CCE1 (Resource7) DL CC2, CCE2 (Resource 4) {−1, −1, 1, −1, 1, 1} DL CC4, CCE1(Resource 7) DL CC3, CCE1 (Resource 5) {−1, −1, 1, −1, 1, −1} DL CC4,CCE1 (Resource 7) DL CC3, CCE2 (Resource 6) {−1, −1, 1, −1, −1, 1} DLCC4, CCE1 (Resource 7) DL CC4, CCE1 (Resource 7) {−1, −1, 1, −1, −1, −1)DL CC4, CCE1 (Resource 7) DL CC4, CCE2 (Resource 8) {−1, −1, −1, 1, 1,1} DL CC4, CCE2 (Resource 8) DL CC1, CCE1 (Resource 1) {−1, −1, −1, 1,1, −1} DL CC4, CCE2 (Resource 8) DL CC1, CCE2 (Resource 2) {−1, −1, −1,1, −1, 1} DL CC4, CCE2 (Resource 8) DL CC2, CCE1 (Resource 3) {−1, −1,−1, 1, −1, −1} DL CC4, CCE2 (Resource 8) DL CC2, CCE2 (Resource 4) {−1,−1, −1, −1, 1, 1} DL CC4, CCE2 (Resource 8) DL CC3, CCE1 (Resource 5){−1, −1, −1, −1, 1, −1} DL CC4, CCE2 (Resource 8) DL CC3, CCE2 (Resource6) {−1, −1, −1, −1, −1, 1} DL CC4, CCE2 (Resource 8) DL CC4, CCE1(Resource 7) {−1, −1, −1, −1, −1, −1} DL CC4, CCE2 (Resource 8) DL CC4,CCE2 (Resource 8)

If

-   2^(M-2)>T^(L),

or resource sharing by different HARQ-ACK bits in one of the two slotsis not desired, or if only a sub-set of the total available resourcesshould be used in order to avoid more frequent than desired errorevents, additional mechanisms can apply for the transmission of

-   M

HARQ-ACK bits. It should be noted that the Node B can choose to increasethe number of CCEs used for the SA transmission in some of the DL CCs inorder to increase the value of

-   L

and satisfy the condition

-   2^(M-2)≦T^(L)

or increase its margin if additional mechanisms are either not availableor not desired.

A second mechanism for increasing the multiplexing capacity of a singleHARQ-ACK signal, in terms of the number of HARQ-ACK bits it can conveyper UE, is to adapt the modulation order of the transmitted signal. Fora single UE transmitter antenna, the necessary condition for supportingthe transmission of

-   M

HARQ-ACK bits over

-   T

distinct resources (no resource is shared in any slot of the sub-framefor the transmission of different HARQ-ACK bits) becomes

-   2^(M-Q)≦T-   where-   Q-   is the number of bits that can be conveyed for a given modulation    order (-   Q=1-   for BPSK,-   Q=2-   for QPSK,-   Q=3-   for 8PSK, and-   Q=4-   for QAM16). For example, assuming-   N=4-   DL CCs with-   K_(j)=4 (j=1, . . . , N)-   CCEs for the SA transmission and 2 TBs transmitted to the UE per DL    CC, the UE needs to transmit-   HARQ-ACK bits over-   T=16-   distinct resources. Using QAM16 modulation, 4 HARQ-ACK bits can be    conveyed and each of the 16 combinations for the remaining 4    HARQ-ACK bits can be accommodated by the UE respectively selecting    one of the 16 available resources, as shown for example in Table 2.

TABLE 2 Mapping of HARQ-ACK Bits to Resources - Single HARQ-ACK SignalTransmission. ACK → −1, NAK → 1 Combinations of Bits DL CC Link of ULResource {1, 1, 1, 1} DL CC1, CCE1 (Resource 1) {1, 1, 1, −1} DL CC1,CCE2 (Resource 2) {1, 1, −1, 1} DL CC1, CCE3 (Resource 3) {1, 1, −1, −1}DL CC1, CCE4 (Resource 4) {1, −1, 1, 1} DL CC2, CCE1 (Resource 5) {1,−1, 1, −1} DL CC2, CCE2 (Resource 6) {1, −1, −1, 1} DL CC2, CCE3(Resource 7) {1, −1, −1, −1} DL CC2, CCE4 (Resource 8) {−1, 1, 1, 1} DLCC3, CCE1 (Resource 9) {−1, 1, 1, −1} DL CC3, CCE2 (Resource 10) {−1, 1,−1, 1} DL CC3, CCE3 (Resource 11) {−1, 1, −1, −1} DL CC3, CCE4 (Resource12) {−1, −1, 1, 1} DL CC4, CCE1 (Resource 13) {−1, −1, 1, −1} DL CC4,CCE2 (Resource 14) {−1, −1, −1, 1} DL CC4, CCE3 (Resource 15) {−1, −1,−1, −1} DL CC4, CCE4 (Resource 16)

A third mechanism for increasing the multiplexing capacity of a singleHARQ-ACK signal (per antenna), in terms of the number of HARQ-ACK bitsit can convey per UE, applies in case the UE has 2 transmitter antennas(with each antenna having its own power amplifier). Then, the number of

-   M

HARQ-ACK bits can be divided among the two antennas with the firstantenna transmitting

-   ┌M/2 ┐

HARQ-ACK bits using, for example, odd numbered UL resources and thesecond antenna transmitting

-   └M/2┘

HARQ-ACK bits using even numbered UL resources, where the

-   ┌ ┐

(ceiling) function rounds a number to its next integer and the

-   └ ┘

(floor) function rounds a number to its previous integer. Then, theavailable UL resources are sufficient for transmitting

-   M

HARQ-ACK bits using a modulation conveying

-   Q-   bits if-   2^(┌M/2┐-Q)≦┌T/2┐-   for the first antenna and if-   2^(└M/2┘-Q)≦└T/2┘-   for the second antenna. For example, for-   T=8-   (such as for-   N=4-   DL CCs with-   K_(j)=2 (j=1, . . . , N)-   CCEs for the SA transmission), if-   M=8-   HARQ-ACK bits need to be transmitted (2 TBs for each of the-   N=4-   DL CCs), the first UE antenna can transmit-   ┌M/2┐=4-   HARQ-ACK bits, using for example QPSK modulation for 2 HARQ-ACK bits    and resource selection for 2 HARQ-ACK bits, and the second antenna    can also transmit-   └M/2┘=4-   HARQ-ACK bits using the same approach as for the first antenna.    Nevertheless, different modulation may be used by each the two UE    transmitter antennas (such as QAM16 for the first antenna and QPSK    for the second antenna). The available resources per antenna are-   ┌T/2┐=└T/2┘=4-   and can accommodate the-   2^(┌M/2┐-Q)=2^(└M/2┘-Q)=4-   combinations of the 2 HARQ-ACK bits conveyed through resource    selection per antenna. Table 3 shows an exemplary allocation of the    odd numbered resources to the first antenna and of the even numbered    resources to the second antenna to convey the value of 2 HARQ-ACK    bits through resource selection.

TABLE 3 Mapping Odd/Even Resources to HARQ-ACK Bits from First/Second UEAntenna. DL CC Link of UL Resources DL CC Link of UL Resources ACK → −1,NAH → 1 for Transmission by First for Transmission by SecondCombinations of Bits UE Antenna UE Antenna {1, 1} DL CC1, CCE1(Resource 1) DL CC1, CCE2 (Resource 2) {1, −1} DL CC2, CCE1 (Resource 3)DL CC2, CCE2 (Resource 4) {−1, 1} DL CC3, CCE1 (Resource 5) DL CC3, CCE2(Resource 6) {−1, −1} DL CC4, CCE1 (Resource 7) DL CC4, CCE2 (Resource8)

A fourth mechanism for increasing the multiplexing capacity of a singleHARQ-ACK channel, in terms of the number of HARQ-ACK bits it can conveyper UE, is to adaptively configure a UE to either use higher ordermodulation, as it was previously described, or to bundle multipleHARQ-ACK bits corresponding to multiple TBs transmitted per DL CC into asingle HARQ-ACK bit. In this manner, UEs with adequately high SINR canstill transmit an HARQ-ACK bit for every received TB using higher ordermodulation while UEs not having adequately high SINR to support higherorder modulation can transmit a single HARQ-ACK bit resulting frombundling the individual HARQ-ACK bits for each TB per DL CC. The bundledHARQ-ACK bit has the value of ACK if all individual bits are ACK and hasthe value of NAK if any of the individual bits is NAK. Bundling ofHARQ-ACK bits per DL CC results to the transmission of a single HARQ-ACKbit per DL CC and

-   M=N.

A fifth mechanism for increasing the multiplexing capacity of a singleHARQ-ACK signal, in terms of the number of HARQ-ACK bits it can conveyper UE per TTI, is to transmit different HARQ-ACK bits in each of the

-   L=2

slots or in each of the two parts of each slot where HARQ-ACK bits aretransmitted. In the first case, the UE transmits the same HARQ-ACK bitsin each slot but different HARQ-ACK bits per slot. In the second case,the UE transmits different HARQ-ACK bits in each half of each slot(using length-2 OCC, instead of length-4 OCC) and the same HARQ-ACK bitsin both slots. Then, the available UL resources are sufficient fortransmitting

-   M

HARQ-ACK bits using a modulation conveying

-   Q-   bits in each slot is-   2^(┌M/2┐-Q)≦T.-   If different HARQ-ACK bits are transmitted is each half of each    slot, then the available UL resources are sufficient for    transmitting-   M-   HARQ-ACK bits using a modulation conveying-   Q-   bits in each slot if-   2^(┌M/4┐-Q)≦T.

Although, for simplicity, the HARQ-ACK signal is assumed to use the samemodulation scheme in each slot or in each half of each slot, this is notnecessary and different modulation schemes may instead be used. Forexample, for

-   T=10

(such as for

-   N=0

DL CCs with

-   K_(j)=2 (j=1, . . . , N)

CCEs for the SA transmission), if

-   M=10

HARQ-ACK bits need to be transmitted (2 TBs transmitted in each DL CC),the first 5 bits can be transmitted in the first slot, or in the firsthalf of the first slot, and the second 5 bits can be transmitted in thesecond slot, or in the second half of each slot, using QPSK to conveythe first 2 of the 5 bits and using resource selection among the

-   T=10

resources to convey the last 3 of the 5 bits in each slot. Table 4 showsan exemplary resource selection to convey 3 HARQ-ACK bits in the firstslot (the same resource selection setup can apply to convey 3 HARQ-ACKbits in the second slot).

TABLE 4 Mapping HARQ-ACK Bits to Resources - HARQ- ACK SignalTransmission in One Slot. ACK → −1, NAK → 1 Combinations of Bits DL CCLink of UL Resource {1, 1, 1} DL CC1, CCE1 (Resource 1) {1, 1, −1} DLCC1, CCE2 (Resource 2) {1, −1, 1} DL CC2, CCE1 (Resource 3) {1, −1, −1}DL CC2, CCE2 (Resource 4) {−1, 1, 1} DL CC3, CCE1 (Resource 5) {−1, 1,−1} DL CC3, CCE2 (Resource 6) {−1, −1, 1} DL CC4, CCE1 (Resource 7) {−1,−1, −1} DL CC4, CCE2 (Resource 8)

Among the previously described mechanisms for the transmission of asingle HARQ-ACK signal, an exemplary decision process in case of asingle UE transmitter antenna is described in FIG. 9 and is as follows:

a) Configure per UE maximum modulation order for HARQ-ACK signaltransmission 910.

b) The UE determines the smallest modulation order satisfying

-   2^(M-Q)≦T

920 and determines if it belongs in the allowable modulation orders theUE is configured 925.

a. If

-   2^(M-Q)≦T

930, the UE transmits the HARQ-ACK signal with the selected modulationorder and using resource selection as it was previously described 940(different combinations of HARQ-ACK bits use different resources in allslots).

b. If

-   2^(M-Q)>T

950 for all allowable modulation orders, the UE can be configured toperform any combination of the following:

i. Allow combinations of HARQ-ACK bits to share the same resource in oneof the

-   L=2

transmission slots 960. Then, the second step is repeated with thecondition

-   2^(M-Q)≦T^(L)

replacing

-   2^(M-Q)≦T.

ii. Bundle multiple HARQ-ACK bits respectively corresponding to multipleTBs received by the UE per DL CC 970. Then, using the new number

-   M_(bundle)

of HARQ-ACK bits resulting after bundling, the second step is repeatedwith the condition

-   2^(M) ^(bundle) ^(-Q)≦T

replacing

-   2^(M-Q)≦T.

iii. Transmit (partly or completely) different HARQ-ACK bits in the

-   L=2

transmission slots 980. Then, the second step is repeated with thecondition

-   2^(┌M/2┐-Q)≦T

replacing

-   2^(M-Q)≦T.

If the UE has 2 transmitter antennas, an exemplary decision process isdescribed in FIG. 10 and is as follows:

a) Configure per UE a maximum modulation order for HARQ-ACK signaltransmission 1010.

b) The UE determines the smallest modulation order satisfying

-   2^(M-Q)≦└T/2┘

1020 and determines if it belongs in its allowable modulation orders theUE is configured 1025.

a. If

-   2^(M-Q)≦└T/2┘-   1030 and the UE is configured transmitter antenna diversity, the UE    signals the HARQ-ACK bits from the first antenna using a first    resource from a first set of resources and signals the same HARQ-ACK    bits from the second antenna using a second resource from a second    set of resources 1035, wherein the first set and second set of    resources do not any common element.

b. If

-   2^(M-Q)>└T/2┘

1040, the UE examines if

-   2^(┌M/2┐-Q)≦┌T/2┐

and

-   2^(└M/2┘-Q)≦└T/2┘

1045.

i. If

-   2^(┌M/2┐-Q)≦┌T/2┐

and

-   2^(└M/2┘-Q)≦└T/2┘

1050, the UE transmits a first HARQ-ACK signal conveying

-   ┌M/2┐

HARQ-ACK bits in a first set of resources using the first transmitterantenna and transmits a second HARQ-ACK signal conveying

-   └M/2┘

HARQ-ACK bits in a second set of resources using the second transmitterantenna 1055, wherein the first set and second set of resources do notany common element.

ii. If

-   2^(┌M/2┐-Q)>┌T/2┐

or

-   2^(└M/2┘-Q)>└T/2┘-   1060, the UE can be configured to perform any combination of the    following:

1. Allow combinations of HARQ-ACK bits to share the same resource in oneof the

-   L

transmission slots (in the exemplary embodiment

-   L=2)

1070. Then, the second step is repeated with the condition

-   2^(M-Q)≦└T/2┘^(L)

replacing

-   2^(M-Q)≦└T/2┘.

2. Bundle multiple HARQ-ACK bits respectively corresponding to multipleTBs received by the UE per DL CC 1080. Then, using the new number

-   M_(bundle)

of HARQ-ACK bits resulting after bundling, the second step is repeatedwith the condition

-   2^(M) ^(bundle) _(-Q)≦└T/2┘

replacing

-   2^(M-Q)≦└T/2┘.

3. Transmit (partly or completely) different HARQ-ACK bits in the

-   L=2

transmission slots 1090. Then, the second step is repeated with thecondition

-   2^(┌M/2┐-Q)≦└T/2┘

replacing

-   2^(M-Q)≦└T/2┘.

While the present invention has been shown and described with referenceto certain preferred embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the presentinvention as defined by the appended claims.

The invention claimed is:
 1. A method for transmitting a set ofacknowledgement bits by a user equipment (UE), the method comprisingsteps of: transmitting, by the UE, a first subset of acknowledgementbits from the set of acknowledgement bits using a first set ofparameters; and transmitting, by the UE, a second subset ofacknowledgement bits from the set of acknowledgement bits using a secondset of parameters, wherein the first subset of acknowledgement bits andthe second subset of acknowledgement bits do not have any commonelements, wherein a union of the first subset of acknowledgement bitsand the second subset of acknowledgement bits is the set ofacknowledgement bits, wherein the first set of parameters includes afirst modulation scheme that is used to transmit the first subset ofacknowledgement bits, and the second set of parameters includes a secondmodulation scheme that is used to transmit a bundled acknowledgement bitrelated to the second subset of acknowledgement bits, wherein thebundled acknowledgement bit has an acknowledgement value if all bits inthe second subset of acknowledgement bits have acknowledgement values,and the bundled acknowledgement bit has a negative acknowledgement valueif at least one bit in the second subset of acknowledgement bits has thenegative acknowledgement value, and wherein the first set of parametersincludes a first duration that is one sub-frame and the second set ofparameters includes a second duration that is different than onesub-frame.
 2. The method of claim 1, wherein the second duration iseither contiguous in a time or non-contiguous in the time.
 3. A methodfor transmitting a set of acknowledgement bits by a user equipment (UE),the method comprising steps of: transmitting, by the UE, a first subsetof acknowledgement bits from a set of acknowledgement bits using a firsttransmission scheme; and transmitting, by the UE, a second subset ofacknowledgement bits from the set of acknowledgement bits using a secondtransmission scheme, wherein the first subset of acknowledgement bitscorresponds to a first subset of scheduling assignments (SAs) from a setof SAs, and the second subset of acknowledgement bits corresponds to asecond subset of SAs from the set of SAs, wherein the first subset ofSAs and the second subset of SAs do not have any common elements, and aunion of the first subset of SAs and the second subset of SAs is the setof SAs, and wherein the first subset of acknowledgement bits transmittedin each of two slots of a subframe are the same, and the second subsetof acknowledgement bits transmitted in each of the two slots of thesubframe are different.
 4. A user equipment (UE) comprising: atransceiver to: transmit a first subset of acknowledgement bits from aset of acknowledgement bits using a first set of parameters; andtransmit a second subset of acknowledgement bits from the set ofacknowledgement bits using a second set of parameters; and a processorto control the transceiver, wherein the first subset of acknowledgementbits and the second subset of acknowledgement bits do not have anycommon elements, wherein a union of the first subset of acknowledgementbits and the second subset of acknowledgement bits is the set ofacknowledgement bits, wherein the first set of parameters includes afirst modulation scheme that is used to transmit the first subset ofacknowledgement bits, and the second set of parameters includes a secondmodulation scheme that is used to transmit a bundled acknowledgement bitrelated to the second subset of acknowledgement bits, wherein thebundled acknowledgement bit has an acknowledgement value if all bits inthe second subset of acknowledgement bits have acknowledgement values,and the bundled acknowledgement bit has a negative acknowledgement valueif at least one bit in the second subset of acknowledgement bits has thenegative acknowledgement value, and wherein the first set of parametersincludes a first duration that is one sub-frame and the second set ofparameters includes a second duration that is different than onesub-frame.
 5. The UE of claim 4, wherein the second duration is eithercontiguous in a time or non-contiguous in the time.
 6. A user equipment(UE) comprising: a transceiver to: transmit a first subset ofacknowledgement bits from a set of acknowledgement bits using a firsttransmission scheme, wherein the first subset of acknowledgement bitscorresponds to a first subset of scheduling assignments (SAs) from a setof SAs; and transmit a second subset of acknowledgement bits from theset of acknowledgement bits using a second transmission scheme; and aprocessor to control the transceiver, wherein the second subset ofacknowledgement bits corresponds to a second subset of SAs from the setof SAs, the first subset of SAs and the second subset of SAs do not haveany common elements, and the union of the first subset of SAs and thesecond subset of SAs is the set of SAs, and wherein the first subset ofacknowledgement bits transmitted in each of two slots of a subframe arethe same, and the second subset of acknowledgement bits transmitted ineach of the two slots of the subframe are different.
 7. A method fortransmitting a set of acknowledgment bits by a user equipment (UE), themethod comprising steps of: transmitting, by the UE, a first subset ofacknowledgement bits using a first transmitter antenna; andtransmitting, by the UE, a second subset of acknowledgement bits using asecond transmitter antenna, wherein the first subset of acknowledgementbits is a response to a reception of one or more scheduling assignments(SAs) for a first cell group, and the second subset of acknowledgementbits is a response to a reception of one or more SAs for a second cellgroup, wherein the first subset of acknowledgement bits is differentfrom the second subset of acknowledgement bits, and wherein a union ofthe first subset of acknowledgement bits and the second subset ofacknowledgement bits is the set of acknowledgement bits that the UEtransmits in a subframe.
 8. The method of claim 7, wherein bits in thefirst subset of acknowledgement bits are respectively transmitted, abundled acknowledgement bit related to the second subset ofacknowledgement bits is transmitted, the bundled acknowledgement bit hasan acknowledgement value if all bits in the second subset ofacknowledgement bits have acknowledgement values, and the bundledacknowledgement bit has a negative acknowledgement value if at least oneof bits in the second subset of acknowledgement bits has the negativeacknowledgement value.
 9. A user equipment (UE) for transmitting a setof acknowledgment bits, the UE comprising: a transceiver to: transmit afirst subset of acknowledgement bits using a first transmitter antenna;and transmit a second subset of acknowledgement bits using a secondtransmitter antenna; and a processor to control the transceiver, whereinthe first subset of acknowledgement bits is a response to a reception ofone or more scheduling assignments (SAs) for a first cell group, and thesecond subset of acknowledgement bits is a response to a reception ofone or more SAs for a second cell group, wherein the first subset ofacknowledgement bits is different from the second subset ofacknowledgement bits, wherein a union of the first subset ofacknowledgement bits and the second subset of acknowledgement bits isthe set of acknowledgement bits that the UE transmits in a subframe. 10.The UE of claim 9, wherein bits in the first subset of acknowledgementbits are respectively transmitted, a bundled acknowledgement bit relatedto the second subset of acknowledgement bits is transmitted, the bundledacknowledgement bit has an acknowledgement value if all bits in thesecond subset of acknowledgement bits have acknowledgement values, andthe bundled acknowledgement bit has a negative acknowledgement value ifat least one of bits in the second subset of acknowledgement bits hasthe negative acknowledgement value.
 11. A method for receiving a set ofacknowledgment bits by a base station, the method comprising steps of:receiving, by the base station, a first subset of acknowledgment bitswhich is transmitted using a first transmitter antenna of a userequipment (UE); and receiving, by the base station, a second subset ofacknowledgment bits which is transmitted using a second transmitterantenna of the UE, wherein the first subset of acknowledgment bits is aresponse to a transmission of one or more scheduling assignments (SAs)for a first cell group, and the second subset of acknowledgment bits isa response to a transmission of one or more SAs for a second cell group,wherein the first subset of acknowledgment bits is different from thesecond subset of acknowledgment bits, and wherein a union of the firstsubset of acknowledgment bits and the second subset of acknowledgmentbits is the set of acknowledgment bits that the UE transmits in asubframe.
 12. The method of claim 11, wherein bits in the first subsetof acknowledgment bits are respectively received, a bundledacknowledgment bit related to the second subset of acknowledgment bitsis received, the bundled acknowledgment bit has an acknowledgment valueif all bits in the second subset of acknowledgment bits haveacknowledgment values, and the bundled acknowledgment bit has a negativeacknowledgement value if at least one of bits in the second subset ofacknowledgment bits has the negative acknowledgement value.
 13. A basestation for receiving a set of acknowledgment bits, the base stationcomprising: a transceiver to receive a first subset of acknowledgementbits which is transmitted using a first transmitter antenna of a userequipment (UE), and to receive a second subset of ACK bits using asecond transmitter antenna of the UE; and a processor to control thetransceiver, wherein the first subset of acknowledgement bits is aresponse to a transmission of one or more scheduling assignments (SAs)for a first cell group, and the second subset of acknowledgement bits isa response to a transmission of one or more SAs for a second cell group,wherein the first subset of acknowledgement bits is different from thesecond subset of acknowledgement bits, and wherein a union of the firstsubset of acknowledgement bits and the second subset of acknowledgementbits is the set of acknowledgement bits that the UE transmits in asubframe.
 14. The base station of claim 13, wherein bits in the firstsubset of acknowledgement bits are respectively received, a bundledacknowledgement bit related to the second subset of acknowledgement bitsis received, the bundled acknowledgement bit has an acknowledgementvalue if all bits in the second subset of acknowledgement bits haveacknowledgement values, and the bundled acknowledgement bit has anegative acknowledgement value if at least one of bits in the secondsubset of acknowledgement bits has the a negative acknowledgement value.